In Vivo Dynamic Lumbar Vertebral Motion and Disc Deformation During Lifting Tasks

描述(由申请人提供)：腰背部疾病(LBD)在美国仍然是最普遍、最虚弱和最昂贵的职业健康问题之一。腰椎的机械负荷是职业性腰椎发育不良的原因和预防的中心因素。现有的评估腰椎(L5-S1)间盘机械力的知识和方法学基础主要来自静态和/或体外身体研究，或来自不确定椎体内部运动或椎间盘变形的体内动态研究。它们在评估与动态工作活动相关的腰背紊乱或损伤风险方面的适用性有限，例如手动举重。我们的主要假设是，更准确地了解腰椎在举重过程中的动态反应将导致更有效地预防和控制腰椎退行性变。这项探索性研究的目的是描述腰椎的动态响应和由负荷和提升运动学(即动态姿势)定义的提升动力学之间的关系，并开始开发一种改进的模型来评估与体力任务相关的腰背部机械应力。这项研究将利用最先进的动态放射成像系统，能够以前所未有的精度在活体测量腰椎运动学，以及我们在研究负荷提升生物力学方面的丰富经验。我们将追求两个具体目标：目标1是描述腰椎运动学和动态提升姿势之间的关系以及提升载荷对这种关系的影响；在提升任务执行过程中，使用动态X光系统获取腰椎运动学数据，使用运动捕捉系统获取全身提升运动学数据。目标2是描述L5-S1椎间盘变形和压缩力分布之间的动态关系；我们将创建一个新的“弹簧加载摆动平台”模型来表征这种关系，并使用从目标1获得的数据来经验地指定它；我们将比较基于新的动态关系确定的L5-S1椎间盘压缩力和通过不考虑动态磁盘变形的传统方法确定的压缩压力。这个拟议的项目是第一次尝试研究腰椎在举重活动中的真正动态和活体机械行为。这将为开发更好的评估或预测动态手动举重过程中下背部机械应力的能力铺平道路。这也将提供一个独特的机会来建立新的椎间盘组织耐受/失败标准(例如，基于体内应变而不是基于应力)。这项工作，以及随后自然会进行的一系列系统研究，将导致新的知识体系和下一代指南、模型和工具，以更好地识别、评估和控制职业性腰椎疾患的风险。 公共卫生相关性：腰椎上的机械负荷是导致和预防腰背部疾病(LBD)的核心因素，LBD是主要的职业健康问题之一。现有的用于评估脊柱负荷的知识和工具是基于对实际工作活动(如负重提升)的相关性和适用性有限的研究。拟议的研究将开发新的科学知识和工具，以便更准确地评估与负重提升任务相关的LBD风险。

DESCRIPTION (provided by applicant): Low back disorders (LBDs) remain one of most prevalent, debilitating, and costly occupational health problems in the United States. Mechanical loading on the lumbar spine is a central factor in the causation and prevention of occupational LBDs. The existing knowledge and methodological bases for evaluating mechanical forces on the lumbo-sacral (L5-S1) inter-vertebral disc were largely developed from static and/or in vitro cadaveric studies, or from in vivo dynamic studies that did not determine the internal vertebral movement or disc deformation. They are limited in their applicability in assessing the low back disorder or injury risks associated with dynamic work activities such as manual load lifting. Our overarching hypothesis is that more accurate understanding of the dynamic responses of lumbar spine during load-lifting will lead to more effective prevention and control of LBDs. The objective of this exploratory study is to characterize the relationships between dynamic responses of the lumbar spine and lifting dynamics defined by the load and lifting kinematics (i.e., dynamic postures), and begin to develop an improved model for evaluating the low back mechanical stress associated with manual tasks. The study will take advantage of a state-of-the-art dynamic radiographic system capable of measuring lumbar vertebral kinematics in vivo with unprecedented accuracy, and our extensive experience of studying the biomechanics of load lifting. We will pursue two specific aims: Aim 1 is to characterize the relationship between lumbar vertebral kinematics and dynamic lifting posture and the effect of load lifted on the relationship; we will acquire data of the lumbar vertebral kinematics using the dynamic X-ray system and the whole-body lifting kinematics using a motion capture system during the performance of lifting tasks. Aim 2 is to characterize the dynamic relationship between L5-S1 disc deformation and compressive force distribution; we will create a novel "spring-loaded wobbling platform" model to characterize this relationship and specify it empirically using data obtained from Aim 1; we will compare the L5-S1 disc compressive forces determined based on the new dynamic relationship and by the conventional approach which does not take into account the dynamic disc deformation. The proposed project is the first attempt to investigate the truly dynamic and in vivo mechanical behavior of the lumbar spine during lifting activities. It will pave the way for developing much improved capabilities to assess or predict low back mechanical stress during dynamic manual lifting. It will also afford a unique opportunity to establish new criteria (e.g., in vivo strain-based instead of stress-based) for disc tissue tolerance/failure. This work, along with a series of systematic studies that would naturally follow, will lead to a new body of knowledge and next-generation guidelines, models, and tools for better recognition, evaluation, and control of the risk of occupational low back disorders. PUBLIC HEALTH RELEVANCE: Mechanical loading on the lumbar spine is a central factor in causing and preventing low back disorders (LBDs) which are one of the leading occupational health problems. The existing knowledge and tools for evaluating the spinal loading are based on studies having only limited relevance and applicability to real work activities such as load lifting. The proposed research will develop new scientific knowledge and tools for more accurate assessment of the risk of LBDs associated with load lifting tasks.